Project Summary Adult stem cells have the ability to produce two daughter cells with distinct cell fates: one capable of self-renewal and the other cell committed to differentiation. Epigenetic mechanisms, which modulate chromatin to differentially express certain genes, play a crucial role in directing cells with identical genomes to take on distinct cell fates. Using a dual-colored strategy to label pre-existing and newly synthesized histones in Drosophila, our lab demonstrated that during asymmetric cell division (ACD) of germline stem cells (GSCs), pre-existing histone H3 is retained in the GSC daughter cell while newly incorporated H3 are segregated to the differentiating daughter cell. In contrast, the histone H3 variant, H3.3, is equally enriched in both cells. What underlies the difference in H3.3 and H3 mechanisms in specifying cell fates during ACD remains unknown. In addition, the differences in H3 and H3.3 during gametogenesis remains unclear. Germ cells, unlike somatic cells, are unique in that they provide a link between generations. One daughter cell undergoes gametogenesis to give rise to the mature sperm and oocyte, which have the capacity to give rise to a whole organism after fertilization. Therefore, the germline is an excellent system to study transmission of epigenetic states during ACD and the cellular differentiation process. The Department of Biology at Johns Hopkins University is an excellent institution to complete this research. The resources to successfully complete the enclosed proposal and fellowship training opportunities at Johns Hopkins University are ideal for post-doctoral training.